Absorption, attenuation, and grids Flashcards Preview

Radiation Physics > Absorption, attenuation, and grids > Flashcards

Flashcards in Absorption, attenuation, and grids Deck (23)
Loading flashcards...
1

PEA results in complete

x-ray absorption

2

compton causes

scatter

3

attenuation

some penetrating x-rays are absorbed by tissues

4

exponential attentuation

absorption depends on tissues thickness

5

HVL measures x-ray

quality/penetrability

6

HVL

thickness of absorbing material needed to reduce x-ray intensity by half

7

types of filtering

1. tungsten anode
2. x-ray tube housing
3. added filtration

8

exposing body parts with unequal thickness

compensatory filter

9

primary bean attenuated by 90%

tenth value layer (TVL)

10

scatter intensity depends on..

kVp, beam field size, and patients thickness

11

grid is a series of

lead strips --> cleans up scatter (up to 80%)

12

grid ratio

R=h/D

13

most frequent grid ratio used

8:1 to 10:1

14

higher ratio grids

less scatter but more radiation exposure is needed

15

paralleled grid flaw

grid cut-of artefact

16

grid cut-off

undesirable absorption of primary x-rays

17

grid cut-off is inversely related to

source image distance (SID)

18

disadvantages of moving grids

bulky mechanism and blurring effect

19

stationary grids mostly used for

portable radio and upright horizontal views

20

higher grid ratio can be met by

increase in mAs

21

mAs should be increased

10% for each cm of air-gap

22

commonly obtained using air-gap technique

lateral cervical

23

used with out grid to reduce scatter and maintain contrast

air-gap technique